THE EFFECTS OF LIGHT

 

LIGHT QUALITY AND PHOTOMORPHOGENESYS

Visible light in the active photosynthetic region (PAR), between 400 nm and 700 nm, provides energy for the photosynthetic process and plant growth, transforming water and carbon dioxide into sugars and oxygen. The spectral composition of light influences all the processes that take place during the life cycle of the plant. This is the reason why the light spectrum is fundamental for the morphology and well-being of the plant. The plants are equipped with different photoreceptors that allow them to respond to different spectra in a different way: phytochrome, cryptochromes and phototropins are only the most studied and understood.

LED technology unlocks the possibility of designing light spectra, mixing single colors and full spectrum sources.




BLUE LEDs (400 - 500 nm)

Blue light is an important component of the light spectrum. It is absorbed by chlorophyll Chl A and Chl B as well as by numerous photoreceptors.

 An increase in the blue component of the light can control the opening of the stomata, inhibit the elongation of the stem and the growth of the leaves and regulate the phototropism (the capacity of the plants to orient themselves according to the light source)

 


WHITE LEDs (400 - 700 nm)

In our systems the green component of light is obtained through the use of white LEDs, which emit between 400 nm and 700 nm. The green composition of this emission (500 nm - 600 nm) can inhibit the excessive effects of blue light as well as stimulate photosynthetic pigments necessary for the correct development of the plant.

 


RED LEDs (600 - 700 nm)

Red light (600 - 700 nm) represents a highly absorbent region for chlorophyll Chl A and Chl B, promotes plant growth and biomass accumulation, stimulates germination and regulates flowering.


LIGHT INTENSITY AND PHOTOSYNTHESIS 

Light reactions such as photosynthesis are activated by the interactions of photons with plant receptors. The intensity of light represents the amount of photons absorbed by the plant on a given surface per second. It is expressed as PPFD (Photosynthetic Photon Flux Density) and is measured in uMol / s / m2. The relationship between light intensity and photosynthesis is well known and understood: the levels of photosynthetic activity increase with increasing light intensity. This is true within a threshold called saturation point. Beyond this limit the photosynthetic activity is limited. It is fundamental to provide the pinate with the right light intensity to obtain an efficient photosynthetic process. It must be considered that not all plant species need the same PPFD, moreover photosynthetic efficiency is closely related to many other factors such as temperature, carbon dioxide concentration and water availability. All these factors influence each other and must be optimized according to the light intensity.


LIGHT QUANTITY AND PLANT GROWTH 

If the intensity can optimize photosynthetic efficiency, the amount of light can do the same with plant growth. When we say quantity we mean the light energy absorbed by plants during a 24-hour period. It is commonly called Daily Light Integral (DLI) and is measured in moles of PAR per square meter per day (mol / m2 / day). The natural photoperiod (the number of hours of light during a period of 24h) changes according to of the season and latitude, as well as weather conditions. Generally, an increase in DLI is directly related to a dry mass increase. In lettuce this can be directly connected to the economic yield. The supplemental greenhouse lighting aims to increase the DLI. The development of specific projects, with lighting simulations and assessments of the available solar resource, is fundamental to obtain the correct levels of intensity. quantity and uniformity in greenhouses.